1. Field of the Invention
The present invention relates to certain compounds which incorporate both o-hydroxybenzophenone (ultraviolet light stabilizer) and hydrazide (heat stabilizer) functional groups.
2. Description of the Prior Art
In addition to activity as a stabilizer on a molar basis (i.e., UV absorber, antioxidant, etc.), a successful stabilizer additive must have both excellent compatibility with and/or solubility in numerous polymer substrates along with superior resistance to loss from the stabilized composition during processing and end-use application. Many stabilizer additives exhibit limited compatibility in certain substrates, and excessive tendency to exude, sublime and/or volatilize during weathering or processing of stabilized compositions, particularly when use conditions require exposure to elevated temperatures. Because of this problem, several attempts have been made to increase the compatibility and reduce the volatility of such stabilizer additives by modifying their structure. While improvements have been noted over the years, experience has shown that state-of-the-art stabilizers do not exhibit the desired combination of properties in all resins and that new polymeric compositions continue to invoke additional structural modifications on any potential heat and/or light stabilizer intended for use. Two examples of this would be in "high solids" coatings which require greater solubility of the stabilizer due to the use of less solvent, and in engineering thermoplastics where processing temperatures (in excess of 250.degree. C.) require the use of stabilizers with high thermal stability and very low volatility. Obviously no one stabilizer to date provides the properties necessary for universal application and there is a constant commercial need for new stabilizers offering a range of property advantages.
Systems which incorporate UV absorbers and other functional groups are known. Multifunctional stabilizers have been prepared by reacting one type of stabilizer with another to obtain a higher molecular weight compound having dual functionality or by reacting two or more stabilizers with a multifunctional coupling agent (e.g. cyanuric chloride) in a stepwise fashion. U.S. Pat. No. 4,481,315 discloses molecular combinations of hydroxybenzophenones and polyalkylpiperidines. Examples of some other stabilization systems contained in one molecule can be found in U.S. Pat. Nos. 3,536,661 and 4,198,334. See Japanese Patent 73/43,658 (Chemical Abstracts, 81: 122589s) which discloses the use of a 2-(2-hydroxyphenyl)-2H-benzotriazole UV absorber and a hydrazide to give enhanced resistance to photodegradation of polyurethane copolymer fibers. None of this prior art discloses the present invention.